Method and apparatus for drying sheet material



Aug. 10 1926.

O. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL Original FiledJan. 20, 1922 5 Sheets-Sheet 1 IAVEgTOR tlnx IORNE Y Xe $40M &

Aug. 10 1926.

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o. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL 5 Sheets-Sheet5 5 lzms zvrolg BY Y 6044a Qifiy A ORNEY Aug, 10 1926. 1,595,480

- 0. MlNTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL OriginalFiled Jan. 2 1922 5 Sheets-Sheet 4 a A/Ja 6 3 a gz 'w fix MW .ORNE Y-Aug. 10 1926, 1,595,480

0. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL orilinal FiledJan. 20, 1922 5 Sheets-Sheet 5 7 ,2 7. 0 Q/ 4 y o f N 0 O O O Y 7 O 2/ 6P7 1261 5 m Patented Aug. 10, 1926.

UNITED STATES OGDEN MINTON, OF GREENWICH, CONNECTICUT.

METHOD AND APPARATUS FOR DRYING SHEET MATERIAL.

- Application filed January 20, 1922, Serial No. 530,665. RenewedFebruary 17, 1926.

The present invention relates to an apparatus and method for the dryingof paper and other sheet materials.

My improved method consists in passing 6 the sheet material, which is tobe dried, intov a vacuum chamber through a liquid sealing medium whichhas no afiinity for the material, subjecting it to heat to drive off itscontained moisture and then passing the dried material out ofthe chamberthrough a seal.

' This method may be practiced by the use of various forms of apparatus,some of which are herein disclosed. In any form, however, it isessential that the apparatus be provided with a closed chamber in whicha partial vacuum may be maintained. In order that the material to bedried may be continuously passed through the. vacuum chamber, the latteris provided with openings closed to the admission of air by a liquidsealing medium which has no allinity for the material. The liquid sealeffectively closes the entrance and exit passages against the admissionof air to the chamber,

' but permits the passage of the material into and out of the chamber.The heating elelnents within the vacuum chamber, for drying thematerial, the shape, form, dimensions and location of the liquid .sealcontainers, and the means for passing the sheet material through thechamber, may all vary.

1 have shown herein a number of varieties which I contemplate using.

This application is a continuation in part of my pending applicationsSerial Nos.

350,233, filed January 8, 1920, Case A, and Ser. No. 384,212, filed May25, 1920, Case J.

The accompanyingdrawings, which are partly diagrammatic, illustrateseveral, but not the only, forms of my apparatus, by the use of which myimproved method may be practiced.

Fig. 1 is a vertical section of one form of apparatus by which myimproved method may be practiced;

Fig. 2 is a vertical section of one of my improved steam doctors;

Fig. 3 is a vertical section of another form provided with onecontainer, for the sealing medium of such shape and dimensions as toreceive revolvingdrums for passing the sheet material:

Fig. 4 is a vertical section of another form similar to that of Fig. 3,provided with endless felts to pass the sheet material through thevacuum chamber;

Fig. 5 is a vertical section on an enlarged scale through a portionofthe felts and sheet material as it passes through the sealing medium ofFig. 4;

Fig. 6 is a vertical section through another form of apparatus, providedwith two vertical containers for the sealing medium;

Fig. 7 is a vertical section of another form provided with only onecontainer for the sealing medium, but with entrance and exit passages;

Fig. 8 is a vertical section of another form provided with endless feltsoperating within the chamber for pressing the sheet material intocontact with the drying drums;

Fig. 9 is a vertical section of another form provided with endless feltsoperating partly within'and partly without the vacuum chamber;

Fig. 10 illustrates a form of apparatus in which the heating medium inthe vacuum chamber consists of a liquid having neither afiinity for nordeleterious efiect upon the material to be dried.

In the form of apparatus, shown in Fig. 1, for practicing my improvedmethod, the vacuum chamber A is formed between the base member B, theupper body member C, and the side walls, not shown. An entrance passageE into the vacuum chamber is formed between the upturned wall D of thebase member and the dependingcurved wall F of the upper body member C,and an exit passage E from the vacuum chamber is formed between theupturned flange D of the base member and the depending curved wall F ofthe upper body member. The entrance and exit passages are sealed againstthe admission of air into the vacuum chamber A, by the liquid sealingmedium 3. I prefer to use mercury for the liquid vacuum seal, butcontemplate any liquid which will effectively seal the openings againstthe admission of air into the chamber, and which has no affinity for thematerial to be dried.

Within the vacuum chamber are mounted rotating drying cylinders 4, 5, 6,7 and 8, and rotatin guide drums 9 and 10. The drying cylinders andguide drums are mounted in any suitable manner and provided with anysuitable means for causing them to revolve at a required speed, and forheating the drying cylinders.

A convenient, but not the only means for passing the sheet materialthrough the vacuum chamber, consists in the system of endless felts,shown in Fig. 1. The upper felt 11 is caused to move, in the directionof the arrows, on the rollers 12 outside the chamber, and, movingthrough the entrance opening E and the liquid seal 3, passes around theguide drum 9 to the drying cylinder 4, to the guide roller 13, to thedrying cylinder 6, to the guide roller 14, to the drying cylinder 8, tothe guide drum 10, through the liquid seal 3 and out of the chamberthrough the exit opening E. The lower felt 15, is caused to move, in thedH'eCtlOll of the arrows, on the rollers 16, 17 outside the chamber,and, moving through the entrance opening E and the liquid seal 3, passesaround the 18, to heating cylin er 5, to guide roller 19, to heatingcylinder 7, to guide roller 20, to guide drum 10, through the liquidseal and out of the chamber through the exit opening E.

In its passage through the drying apparatus, the web 1 of paper, orother sheet material, is fed between the felts 11 and 15 and passesbetween the felts partly around drum 9, the web 1 with the felt 11passing up to cylinder 4 and the felt 15 passing to roller 18. As thewet web tends to cling to the felt, means 22 may be provided, ifdesired, at this point to strip the web 1 from the felt 15 and direct itagainst the felt 11 which with the web 1 passes around cylin der 4, thefelt passing to roller 13 and the web, which also tends to cling to theheated surface of the cylinder, may be caused to leave both surfaces andto descend and be caught between the felt 15 and the surface of thecylinder 5. Moving around cylinder 5 the felt 15 moves to roller 19. Theweb 1 may be caused to leave the felt and the heated surface of thecylinder 5 and to ascend and be caught between the felt l1 and theheated surface of cylinder 6. To over come the tendency of the web tocling to the felts and the heated surfaces of the cylinders and to guidethe passage of the end of the web from one cylinder to the next inadvance in the series, and particularly from one below to the nextabove, I may use the steam doctors 22.

One form of steam doctor is shown in Fig. 2 so located as to strip theweb from a cylinder 7 and then direct the web in an upward direction.Preferably the doctor is of suflicient length to extend across thecylinder, at least to cover the width of the web and felts. It isprovided with a steam supply passage 26, from which extends the port 27to the toe 28, and the ports 30, 31

uide drum 9 to roller and 32, leading upward toward the head 33 When thedoctor is mounted near a heating ploy them the steam issuing from thedoctors dries the end of the web and makes it firm so that the web canbe more readily threaded through the apparatus. If a steam doctor isemployed the steam from the doctor also assists in drying the web inpassing through the vacuum chamber.

To assist, if desired, the passage of the web from one cylinder to thenext cylinder in advance, I may locate one doctor near the cylinder andanother on the opposite side of the web near the felt. The toe jets 27in each doctor will strip the web from surfaces of the cylinder and feltand the body jets 30, 31 and 32 impinging on both sides of the web willassist in directing its movement and carry the end of the web forward tothe next cylinder.

be carried upward from one cylinder to the next in the series locatedabove. a

In Fig. 3 the wet web 1 passes-into the "acuum chamber A through theentrance passage E over the guide roller 36 under the submerging roller37 in the liquid seal thence in contact with rotating guide drum 9,rotating drying cylinders 4, 6 and 8, then over the rotating guide drum10 through the seal 3, under the submerging roller 38 and out throughthe exit passage E and then over the guide roller 39.

In this form of my invention the web 1 is dried by direct contact Withthe rotating drying cylinders l, 6 and 8, and also the rotating guidedrums 9 and 10 should these be heated, without the aid of a felt orfelts.

I preferably arrange the rotating guide drums 9 and 10 partiallysubmerged as shown for if a web of paper is fed through a sealing mediumunsupported, it has a tendency to wave and flap. If this Waving andflapping is suflicient for the web to engage with the fixed nonmovingportion of the Vacuum chamber, the web is apt to cling to or be retardedby the fixed surface of the chamber with which it contacts. This willcause a break in the web or broke. This serves to foul the machine,requiring rethreading and delays which are very ex- This is adv\'antageous where the end of the web must llh pensive in the manufactureof paper, as

time is one of the most important factors.

Even if the waving or flapping of the web, while passing through theliquid seal and before it is taken u by one of the drying cylinders, isnot su cient to cause it to engage with the side of the sealing chamberwhich might break the web, it causes the fibers to rearrange themselvesso that when the paper is dried it has an undesirable crinkle. Thiscrinkle is more or less pronounced depending upon the a" iount of thewaving or flapping of the web in its'passage into the vacuum apparatusBy my invention the web 1 is fed almost immediately on its entrance intothe liquid seal 3 into contact with the rotating guide drum or cylinder9, which is traveling at the same rate of speed as the web. The web willcling to this guide drum during its vertical passage through the sealand until it emerges from the liquid seal 3, in the vacuum chamber A,when almost immediately it passes onto the first of the dryers .4, sothat there is no waving or flapping of the web and consequently theliability of Broke from this cause is practically obviated. Theundesirable crinkling of the paper is also prevented. Mounting therotating guide drums so as to be partially submerged in the liquid sealnecessitates using only a comparatively little sealing medium 3.

In Fig. 4, I have shown substantially thesame form of apparatus asillustrated in Fig. 3, except that the web 1 is fed over and around therotating guide drums 9 and 10 and the rotating drying cylinders 4, o and8.by means of the upper felt 11 and the lower felt 15.

Both felts 11 and 15 meet at the entrance passage E and receive the wetweb 1 between them. They then, with the interposed web 1, passthrough-the seal 3 over the rotating guide drum 9. The upper felt 11,with the web 1, then passes over the rotating drying cylinder 4, the webbeing in contact with the cylinder. In leaving the cylinder 4 the web 1contacts with the drying cylinder 6 being pressed into contact with itby the lower felt 15 which after leaving the drum 9 passes over theguide rollers 41, 42, thence around the rotating guide drum 10,submerging roller 38, out through the exit passage E, over the guiderollers 17, 16

back to the entrance passage E to again engage with the web 1.

The upper felt 11 after passing over the rotating drying drum 4 is ledover, but not in contact with, the rotating drying cylinder 6 by passingover the guide rollers 43, 44, 45 and 46, thence around the rotatingdrying drum 8 in contact with the web 1, thence over the rotating guidedrum 10 under the submerging roller 38, out of the exit passage E andover the guide rollers 47 and 48 back to the entrance passage E.

It will, therefore, be seen that in this form of my invention the web 1passes over the rotating guide drums 9 and 10 interposed between thefelts 11 and 15, but in passing over the rotating drying cylinders 4, 6and 8 it contacts directly with each of said drying cylinders.

Figs. 6, 8 and 9 illustrate other forms of drying apparatus in which thebase B is provided with sealing medium containers X formed by verticalwalls Y, the U-shaped entrance passage E and exit passage E .to and fromthe vacuum chamber being formed between the vertical walls of thecontainers and the depending flanges P of the body member C.

In this form of my invention the web 1 passes over the guide roll 36through the entrance passage E into the liquid seal 3 under thesubmerging roll 37 and up into the vacuum chamber and in contact withthe rotating heated drying cylinders 4, 5, 6, 7 and 8 and out throughthe exit seal 103 under the submerging roller 38 over the guide roller39. and is then preferably immedis-jely rolledinto a finished roll orreel of paper 48.

In Fi 7 is shown a form of vacuum drier provided with a single sealingmedium container X, the entrance and exit passages to and from thevacuum chamber belng provided between the vertical walls Y of thecontainer and the depending flanges P of the body member C.

In Fig. 8 both the lower endless felt 15 and the upper endless felt 11are within the vacuum chamber A and do not pass out through the entranceand exit 1i uid seals 3 and 103 respectively, as in someo the otherforms o my invention. The lower felt 15 presses the web 1 against therotating drying cylinders 5 and 7 and passes over the guide rollers 49,50, 51, 52 and 53. The upper felt 11 presses the web 1 into contact withthe rotating drying cylinders 4, 6 and 8, and passes over the guiderollers 54, 55, 56, 57, 58 and 59.

In Fig. 9, I have shown a form of my invention similar to Fig. 8 exceptthat the endless felts 11 and 15 pass into and out of the vacuum chamberA with the web 1 through the entrance and exit passages E and E,respectively, and through the liquid seals 3 and 103 respectively,protecting each of said passages. After passing under the submergingroller 37 both upper and lower felts, with the interposed web 1, pass upto the guide rollers 60 and 61. The web 1 and the upper felt 11 passover the rotating drying cylinder 4,the felt pressing the web intocontact with the drying cylinder. The

web 1 then passes over the drying cylinder 5, cooperating with the lowerendless felt 15. It then passes overthe drying cylinder 6 while incontact with the upper endless felt 11. this felt having passed over theguide rollers 62, 62. The upper felt passes around the drying cylinders6 and 8 and then in lot contact with theguide roller 65, submergingroller 38, guide rollers 66, 66 back to the entrance passage E, Thelower felt after )tISSlIIg over the guide rollers 63, 63 rotating ryingcylinder 7, guide roller 64, submerging roller 38 and guide rollers 39,and 67, 67 again passes over the guide roller 36.

Fig. 10 illustrates a form of my vacuum drier, in which the heatingmedium for drying the sheet material consists preferably of t acteristicof the so-called loft d1 1n mercury or of any other liquid havingneither affinity for, nor deleterious effect upon, the material. Asshown, the liquid iscontained within the vacuum chamber, separated fromthe sealing medium, and is heated byany suitable means. I have shown adevice for passing the sheet material through the liquid seals and thenthrough the liquid heating medium. The apparatus shown in Fig. 10 isparticularly useful in the manufacture of high grade papers.

In this illustrative embodiment of my invention the web 1 passes overthe guide cylinder 36, into the entrance passage E beneath thesubmerging roller 37 in the liquid seal 3, thence into the vacuumchamber A over the guide rollers 69, 70 and then into the heating liquidbath 71 under the roller 72, thence out over the guide rollers 73, 74through the exit liquid seal 3 under the subnierging roller 38 and outof the exit passage E. over the guide roller 39, where the web ispreferably, though not necessarily, immediately rolled into the finishedroll of paper 48.

The roller 7 2, may or may not be heated. Preferably the mercury orequivalent liquid bath 71 is heated by passing steam, products ofcombustion or other source of heat through the passage 75.

The liquid of the seals 3, 3 may be heated if desired by any suitablemeans as by steam pipes 76, 76 though these, of course, may be omittedwithout departing from my invention.

In all forms of my invention the vacuum chamber A is connected withpipes 77, 77, leading to any suitable vacuum apparatus to maintain apartial vacuum. in the Vacuum chamber.

I also preferably provide the casing C of the vacuum chamber with one ormore windows 78 that the operator may at all times see within thechamber.

My improved method, particularly adapted, though not confined, to thedrying of paper, consists in taking the wet web of paper as it comesfrom the paper making machine, and either before or after sizing orcoloring the web, passing the Web into a vacuum chamber through asealingmedium,having neither affinity for, nor del eterious effect upon, thematerial of the web, and subjecting it while in the .vacuum to directcontact, with the heated surface of rotating cylinders, or with a liquidhaving neither aflinity for, no deleterious effect upon, the material,whereby the contained moisture is driven off, and then passing the drymaterial out of the chamber through the sealing medium.

My method possesses many advantages not present in processes heretoforeused for many years in the drying of paper.

The evaporation process, which is char 0 paper, has many fully recognizedisadvantages, and yet it is used today and has been in use for manyyears. In this method the wet paper is taken from the paper machine, cutinto sheets, hung on poles, carried to the drying room where it issubjected to hotair at about 130 F. for about 48 hours, and when dry,each sheet is separately ealendered. Although possessing the advantageof drying at a comparatively low temperature, whereby the moisture isslowly evaporated, loft drying is obviously very inefficient and costly,because it requires many separate manipulations, is extremely slow, usesextensive floor space and wastes heat.

The process which is employed in the ordinary paper machine in commonuse, is likewise subject to many disadvantages. In such machine, the wetpaper as it comes from the paper machine, is passed over many revolvingcylinders, heated internally by steam to sufficiently high degree ofheat, to raise the temperature of the water in the paper to 212 F.. theatmospheric boiling point of water. It is customary to supply the dryingcylinders with steam at approximately 5.3 pounds gauge pressure, atwhich the steam has a temperature of 228 F. giving a difference oftemperature (228- 212) of only 16 F. With this slight difference oftemperature the transfer of heat is extremely slow, and hence it isnecessary to employ many drying cylinders, in board machines often onehundred, and in news print machines, forty or more.

Also due to convection and conduction losses, as well as those incidentto leaks in the piping system and other inefliciencies, the heatactually required for atmospheric drying of a ton of wet paper, is verymuch in excess of the theoretical requirement. The thermal efliciency ofatmospheric drying by steam heated cylinders is therefore very low.Furthermore, the steam produced from boiling the water out of the paper,is driven off into the operating room. and although fans and exhaustersare em ployed, at large expense for power and maintenance, the roomatmosphere. is so constantly saturated with moisture as to rust andultimately destroy all iron and steel materials, and produces anexceedingly disagreeable and unhealthy atmosphere in which to work. Itis well' known that the minimum temperature 212, the atmospheric boilingpoint of water, is positlvely injurious to, and results in oxidizing,the fibres of the paper, the strength of which is vastly improved whenthe paper 1s dried at lower temperatures, as in loft drying. Thisatmospheric dryin process requires large initial cost for cy inders,felts, and

other necessary equipment, and extensive floor space, and results in theconsumption of large amount of power, and great cost for operation,maintenance and repairs.

Some of the modern open air driers are equipped with a blower system bywhich air, either heated or not, is blown throu h the dryer sections,which will lower t e temperature at which the water is evaporated fromthe paper much below 212 F. and may, in some cases, reduce thetemperature of evaporation as low as 180 F. or lower.

In my improved vacuum drying method I contemplate maintaining within thechamber a vacuum of about 28" of mercury, in which water boils at 100F., and

' supplying the drying cylinders with steam at 5.3 pounds gaugepressure, producing a temperature of 228 F. the temperature differencebetween the temperature of the steam in the cylinders and that of thepaper, is therefore, 128 F. in my vacuum method, or 8 times greater (16F. 8= 128 F.) than the temperature difference in atmospheric dryin In myimproved method the paper dries approximately 8 times faster than inatmospheric drying, and I require only about one-eighth the number ofdrying cylinders to dry paper at 4 the same rate of speed. I am able todry paper with 5 cylinders in the sametime required of 40 cylindersdrying at atmospheric pressure, resulting in great economies in cost ofthe machine, floor space and of necessary piping, felts, auxiliaryequipment, and particularly in power and maintenance charges.-

The thermal efficiency of my vacuum method is very much greater thanthat of at atmospheric cylinder drying heretofore in universal use fordrying paper. Theoretically, it requires about 5287 pounds of steam todry one ton of paper at atmospheric pressure, but to compensate forconvection and conduction losses, and those due to leaks in the pipingsystem, and other ineificiencies, it has been shown in practice thatabout 10,600 pounds are required.

In my method, using a vacuum of about 28", the convection, conductionand piping losses are exceedingly small and the total steam required todry 1!. ton of paper by my .method is approximately 5200' pounds.

It is an established fact that paper dried still produce a paper equalin stren h to atmospheric dried paper, in which a igher grade furnish orstock is used. In making newsprint paper, I amab-le to dispense with aconsiderable portion of the more expensive sulphite pulp, as this can bereplaced with the chea er ground wood pulp. By my method I also reducethe number of breaks in the web as it passes over the cylinder.

Furthermore, in my method there is a great saving of heat (or steam)because the process is carried on in a vacuum chamber which acts on theprinciple of a thermos bottle, and the steam and vapors driven out ofthe wet pa or are caughtin the closed vacuum cham er, and conducted awayto the condenser. The operating room is free from steam, humidity andheat, and fans, and exhausters are dispensed with. In the use of mymethod the apparatus is at all times operating under definite humidity,the control of the drying can be closely standardized, and the moisturecontent in the paper carefully regulated.

Having pointed out the many advantages of my method and apparatus overthose heretofore used, it will be apparent that the use of my inventionresults in great economy in the initial cost of apparatus and in largesavings in cost of operation, maintenance and repairs.

Having thus described this invention in connection with illustrativeembodiments thereof, to the details of which I do not desire to belimited, what is claimed as new and what is desired to secure by LettersPatent is set forth in the appended claims.

What I claimis:

1. The method of drying sheet material which consists in passing the wetuncoated sheet material into a vacuum chamber through a liquid sealingmedium which has no affinity for the sheet material, subjecting thesheet material in the vacuum chamber to a separate body of heated liquidhaving no afiinity for the sheet material, and passing the sheetmaterial out through a sealing medium.

2. The method of drying sheet material which consists in passing the wetuncoated sheet material into a vacuum chamber through a liquid sealingmedium which has no afiinity for the sheet material, subjecting thesheet material in the chamber to the surface of a heated cylinder, andpass ing the sheet material out through a sealing medium.

3. The method of drying sheet material which consists in passing the wetuncoated sheet material in contact with one or more endless felts into avacuum chamber through a liquid sealing medium which has no aflinity forthe sheet material, subjectlng the sheet material in the'vacuum chamberto heat to drive off the contained moisture, and passing the felts andthe dry material out through a sealing medium.

4. The method of drying sheet material which consists in passing the wetuncoated sheet material in contact with one or more endless felts into avacuum chamber through a liquid sealing medium which hasno affinity forthe sheet material, sub ecting the sheet material in the vacuum chamberto heat and to the stripping action of steam ets to strip the wet sheetmaterial from felts and driers and direct its movement, and passing thefelts and dry sheet material out through a sealing medium.

The method of drying paper which consists in passing the web of paperinto a vacuum chamber through a sealing medium which has no affinity forthe paper, subjecting the paper in the vacuum chamber to heat and to thestripping action of steam jets to strip the paper from felts and driersand direct its movement, and passing the dry paper out through a sealingmedium.

6. The method of drying paper which consists in passing the web of paperin contact with one or more felts into a vacuum chamber through a liquidsealing medium which has no aflinity for the paper, subjecting the paperin the vacuum chamber to heat and passing the dry paper out through asealing medium.

7. The method of drying paper which consists-in passing the web of paperin contact with one or more felts into a vacuum chamber through asealing medium which has no afiinity for the paper, subjecting the,paper in the vacuum chamber to heat and to the stripping action of steamjets to strip the paper from felts and driers and direct its movement,and passing the dry paper out through the sealing medium.

8. The method of drying paper which consists in passing the web of paperin contact with one or more felts into a vacuum chamber through amercury seal, subjecting the paper in the vacuum chamber to heat todrive off the contained moisture, and passing the felts and dry paperout through a mercury seal.

9. The method of drying paper which consists in passing the Web of paperin contact with one or more felts into a vacuum chamber through amercury seal, subjecting the paper in the vacuum chamber to heat and tothe action of steam jets to strip the wet sheet material from felts anddriers and direct its movement, and passing the d paper and felts outthrough a mercury sea 10. An apparatus for drying sheet materialcomprising a closed chamber having entrance and exit passages, means toform a partial vacuum in the chamber, a liquid seal for said passageswhich has no atlinity for the sheet material, and means located withinthe chamber and spaced away from the liquid seal for heating the sheetmaterial.

11. An apparatus for drying sheet material comprising a closed chamberhaving entrance and exit passages, means to form a partial vacuum in thechamber, a liquid seal for said passages which has no afiinity for thesheet material, one or more cylinders within the chamber for heatingthesheet material, and means for heating the cylinders.

12. An apparatus for drying sheet material comprising a closed chamberhaving entrance and exit passages, means to form a partial vacuum in thechamber, a liquid seal for said passages which has no afiinity for thesheet material, a liquid within the chamber separate from said liquidseal and having no aflinity for the sheet material, means for heatingthe said liquid and means for passing the sheet material through saidheating liquid.

13. An apparatus for drying paper comprising a closed chamber havingentrance and exit passages, means to form a partial vacuum in thechamber, a mercury seal for said passages and Ireans located within thechamber and spaced away from the mercury seal for heating the paper.

sisting of a vacuum chamber and liquid sealing means through which thematerial passes into and out of said vacuum chamber, the liquid of saidsealing means having no afiinity for the sheet material, and one or moreheated drying cylinders mounted in the vacuum chamber.

15. An apparatus for drying sheet material consisting of a vacuumchamber and mercury sealing means throu h which the material passes intoand out 0 said vacuum chamber, and one or more heated drying cyl indersmounted in the vacuum chamber.

16. An apparatus for drying sheet material consisting of a vacuumchamber and liquid sealing means through which the material passes intoand out of said vacuum- 14. An apparatus for drying paper conliquidsealing means through which the material passes into and out of saidchamber, the liquid of said sealing means having no affinity for thesheet material, endless felts for passing the sheet material through thesaid vacuum chamber, means for directing the endless felts, and one ormore heated drying cylinders mounted in the vacuum chamber.

18. An apparatus for drying sheet material consisting of a vacum chamberand liquid sealing means through which. the material passes into. andout of said chamber, the liquid of said sealing means having no afiinityfor the sheet material, endless felts for passing the sheet materialthrough the vacuum chamber, one or more heated drying cylinders mountedin the vacuum chamber, and means within the chamber for directing jetsof steam against the sheet material to strip it from said felts anddrying cylinders and direct its movement.

19. An apparatus for dryin sheet material consisting of a vacuum c amberand mercury sealing means through which the material passes into and outof said chamber, endless felts for passing the sheet material throughthe vacuum chamber and one or more heated drying cylinders mounted inthe vacuum chamber.

20. An apparatus for drying sheet material consisting of a vacuum'chamber and mercury sealing means through which the material passes intoand out of said chamber, endless felts for passing the sheet materialthrough the vacuum chamber, a heating liquid within said vacuum chamberhaving no affinity for the sheet material which is passed through it,and means for heating said liquid.

21. An apparatus for drying sheet material consisting of a vacuumchamber and mercury sealing means through which the material passes intoand out of said vacuum chamber, endless felts for passing the sheetmaterial through the vacuum chamber, one or more heated drying cylindersmounted in the vacuum chamber, and means within the chamber fordirecting jets of steam against the sheet material to strip it from saidfelts and drying cylinders and direct its movement.

22. The method of drying a web of paper consisting in passing it into avacuum chamber through a liquid seal which has no affinity for said web,passing the web while in the chamber over one or more revolving heateddrying drums to dry, flatten, and give a smooth finish to the web,pressing said web of paper into contact with said heated drying drums,and thenpassing said dry, flat and smooth web of paper out of thechamber through a liquid seal which has no aflinity for said web.

23. The method of drying paper consisting in passing the web of thepaper in contact with one or more endless felts into a vacuum chamberthrough a liquid sealing unedium which has no affinity for, ordeleterious efiect upon the paper, drying said web in said vacuum andwithdrawing the dry web of paper and the felts from the vacuum chamberthrough a liquid sealing medium having the same charactertistics as thatfirst mentioned.

- OGDEN MINTON.

